The role of increasing temperature variability in European summer heatwaves

Analyzes instrumental observations and reconstructions of global and hemispheric temperature evolution, which reveal a pronounced warming during the past 150 years

States that one expression of this warming is the observed increase in the occurrence of heatwaves, understood conceptually as a shift of the statistical distribution towards warmer temperatures, while changes in the width of the distribution are often considered small

Shows that this framework fails to explain the record-breaking central European summer temperatures in 2003, although it is consistent with observations from previous years

Finds that an event like that of summer 2003 is statistically extremely unlikely, even when the observed warming is taken into account

Proposes that a regime with an increased variability of temperatures (in addition to increases in mean temperature) may be able to account for summer 2003

Simulates possible future European climate with a regional climate model in a scenario with increased atmospheric greenhouse-gas concentrations, and find that temperature variability increases by up to 100%, with maximum changes in central and eastern Europe